r15734: This is a major change to the NTVFS subsystem:

r15734: This is a major change to the NTVFS subsystem:

- to use a struct ntvfs_handle instead of a uint16_t fnum.
  (to make it independend from the frontend protocol)
- the allocation of handles now is provided by the frontend
  (smbsrv_*) via callbacks and not by each backend module
- this also makes sure that file handles are only passed
  to the ntvfs subsystem when the tcon and session matches,
  so modules can rely on this and need to check this.
- this allows multiple modules in the ntvfs module chain
  to allocate file handles. This can be used for virtual
  files like "\\$Extend\\$Quota:$Q:$INDEX_ALLOCATION"...
- also this will make SMB2 with 128 bit file handles possible

metze